A regularly scheduled inspection of the manufacturing line is completed and has noted that a key piece of machinery is showing signs of wear and damage much earlier than expected. A change request has been submitted to be reviewed by the Change Control Board to interrupt product manufacturing in order to replace the damaged parts of machinery. This unscheduled repair will take the entire manufacturing line down for two weeks. Without the repair the machinery could fail and cause more extensive damage resulting in a much longer and more expensive work stoppage. The CCB approves the change request and schedules the repair work to be completed as soon as possible. This is best described as: a. Corrective actionb. Defect repairc. Preventive actiond. Monitoring and Controlling Project Work

tricky part is its just showing sign of wear and tear but nothing has happened yet.Production lines are working fine. no production failures. so there is no defect as such as of now . Because of wear and tear some problem is going to happen in future is not a characteristic of defect. Question is telling "Without the repair the machinery could fail ". means there is no defect as such as of now

SO now What you did is that you have pro-actively taken precaution which is actually preventive.